We propose to clinically evaluate the ability of a novel intracardiac ARFI ultrasound imaging system combined with an electro-anatomic mapping system to guide radio-frequency ablations procedures for treating atrial fibrillation and atrial flutter. In parallel, and in collaboration with our industrial partner Siemens Ultrasound, we will migrate these technologies to a 3D ultrasonic imaging platform and develop two intracardiac probes optimized for combined 3D B-mode/ARFI imaging. Phantom, animal and, ultimately, human studies are proposed to evaluate the 3D scanner/probes and the related pulse sequences, beam forming methods and signal and image processing methods to be developed. If successful, the proposed methods will provide the electrophysiologist with real-time visualization of cardiac ablation lesions and with the ability guide the creation of these lesions. As such, the proposed studies could markedly reduce treatment times for atrial and ventricular cardiac ablation procedures, prevent complications from over ablation and reduce the rates of repeat procedures. PUBLIC HEALTH RELEVANCE: We propose to move from the laboratory to the clinic the technique we developed in Phase I for image guided ablation therapy. This system can show the physician regions of the heart which have already been treated. Currently physicians have no means to examine these regions. In Phase I we successfully built the system and demonstrated its efficacy. In phase II we plan a series of clinical tests to demonstrate its utility for treating atrial arrhythmias in patients.